Multi-metallic catalyst doped with phosphorus and yttrium

ABSTRACT

The invention relates to a catalyst comprising a support, at least one noble metal M, tin, phosphorus and yttrium, the content of phosphorus element being less than or equal to 1% by weight, and the content of yttrium being less than or equal to 1% by weight relative to the mass of the catalyst. The invention also relates to the process for preparing the catalyst and to the use thereof in reforming.

The present invention relates to the field of hydrocarbon conversion andmore specifically to the reforming of hydrocarbon-based feedstocks inthe presence of a catalyst to produce gasoline cuts and aromaticcompounds. More particularly, the invention relates to an improvedcatalyst based on at least one noble metal, tin, phosphorus and yttrium,to the process for preparing same and to the use thereof in a reformingprocess.

Catalytic reforming processes make it possible to significantly increasethe octane number of gasoline fractions originating from the directdistillation of crude oil and/or from other refining processes, forinstance catalytic cracking or thermal cracking. The process ofcatalytic reforming is a process that is very widely used by refiners inorder to upgrade the heavy gasoline obtained by distillation. Thehydrocarbons of the heavy gasoline feedstock (notably paraffins andnaphthenes) containing from 5 to 12 carbon atoms approximately permolecule are converted during this process into aromatic hydrocarbonsand branched paraffins. This conversion is obtained at high temperature(on average in the range 480 to 520° C.), at low to medium pressure (0.2to 2.5 MPa) and in the presence of a catalyst. Catalytic reformingproduces reformate which makes it possible to significantly improve theoctane number of petroleum cuts, and hydrogen. Reformate ispredominantly formed of C5+ compounds (compounds containing at least 5carbon atoms).

Reforming catalysts are multi-metal catalysts. There are two majorcategories of reforming catalysts, which have different properties:platinum-tin catalysts generally used in the form of beads in amoving-bed reactor in CCR (continuous catalytic reforming) processes,and platinum-rhenium catalysts generally used in extruded form in fixedbeds.

For these two types of catalysts, numerous patents describe the additionof promoters in order to improve their performance with regard to thereforming of hydrocarbon-based feedstocks.

As regards doping with lanthanides, and notably cerium, U.S. Pat. No.2,814,599 describes the addition of promoters such as gallium, indium,scandium, yttrium, lanthanum, thallium or actinium, to catalysts basedon platinum or palladium. US 2013/0015103 describes catalysts with Ce(PtSnCe). US 2013/0256194 describes this same type of catalyst incombination with alkaline compounds in very low content. EP 1390140describes catalysts doped with Ce and/or Eu. CN103372454 and U.S. Pat.No. 6,239,063 describe catalysts including other lanthanides in additionto Ce on the same catalyst. CN105771981 claims the combined use of Ceand Y on the same catalyst of PtSn type.

Phosphorus is moreover known for increasing the yields ofhydrocarbon-based compounds strictly containing more than 4 carbon atoms(C5+) and in particular of aromatic products. This property is claimedin U.S. Pat. Nos. 2,890,167, 3,706,815, 4,367,137, 4,416,804, 4,426,279and 4,463,104.

US 2012/122665 describes a catalyst comprising platinum, tin, phosphorusand at least one promoter selected from the group consisting of gallium,indium, thallium, arsenic, antimony and bismuth.

EP1656991 describes a catalyst comprising platinum and tin with a Pt/Snratio of less than 0.9, and optionally another element chosen fromgermanium, gallium, cerium, lanthanum, europium, indium, phosphorus,nickel, iron, tungsten, molybdenum, zinc and cadmium, alone or as amixture in an elemental content of between 0.1% and 10% by weightrelative to the mass of the catalyst, without, however, linking anyparticular effect to the promoters.

It has also been described in US 2007/0215523 that the addition ofdilute amounts of phosphorus, less than 0.4% by weight, stabilizes thesupport by allowing better specific surface area retention and chlorineretention during its use in catalytic reforming processes. Said documentdiscloses a catalyst based on platinum and phosphorus optionallycomprising another element chosen from tin, rhenium, germanium, lead,indium, gallium, iridium, lanthanum, cerium, boron, cobalt, nickel andiron, alone or as a mixture in an elemental content of between 0.01% and5% by weight relative to the mass of the catalyst.

In this context, one of the objects of the present invention is topropose a catalyst which has improved selectivity and stability in areforming process without deteriorating the activity.

The term “selectivity” means the yield of C5+ compounds expressed as amass percentage relative to the effluent at a given level of activity(typically at a given octane number level).

The activity is generally characterized as the given octane number ofthe C5+ compounds at a level of severity or is expressed, conversely, bya temperature required to reach a given octane number (also known as theRON or Research Octane Number).

The term “stability” means the stability of the activity which isgenerally measured by the thermal increment applied during functioningin the unit per unit of time or of feedstock to maintain the performanceat a given octane number.

The invention relates to a catalyst comprising a support, at least onenoble metal M, tin, phosphorus and yttrium, the content of phosphoruselement being less than or equal to 1% by weight, and the content ofyttrium being less than or equal to 1% by weight relative to the mass ofthe catalyst.

It has been shown that the simultaneous presence of a phosphoruspromoter and of an yttrium promoter, each promoter being present in acertain amount on a catalyst based on a noble metal and tin, gives thefinal catalyst selectivity and stability that are far superior to thoseof the prior art catalysts containing only one of these promoters.Without being bound to any theory, it appears that the simultaneouspresence of an amount of a phosphorus promoter of less than or equal to1% by weight, preferably between 0.3% and 1% by weight and even morepreferably between 0.4% and 0.8% and of an amount of an yttrium promoterof less than or equal to 1% by weight, preferably between 0.01% and 0.5%by weight relative to the mass of the catalyst, shows, surprisingly, asynergistic effect on improving the selectivity and the stabilitywithout this synergistic effect being foreseeable by the simple additionof the known improving effects of the promoters.

According to one variant, the content of noble metal M is between 0.02%and 2% by weight relative to the mass of the catalyst.

According to one variant, the metal M is platinum or palladium.

According to one variant, the content of tin element is between 0.005%and 10% by weight relative to the mass of the catalyst.

According to one variant, the yttrium content is between 0.01% and 0.5%by weight relative to the mass of the catalyst.

According to one variant, the phosphorus content is between 0.3% and 1%by weight relative to the mass of the catalyst.

According to one variant, the Sn/M atomic ratio is between 0.5 and 4.0,the P/M ratio is between 0.2 and 30.0 and the Y/M ratio is between 0.1and 5.0.

According to one variant, the support comprises silica, alumina orsilica-alumina.

According to one variant, the catalyst also contains a halogenatedcompound.

According to this variant, the content of halogenated compound isbetween 0.1% and 8% by weight relative to the mass of the catalyst.

The invention also relates to a process for preparing a catalystaccording to the invention, comprising the following successive steps:

-   -   a) a precursor comprising a support, tin, phosphorus and a noble        metal is prepared,    -   b) the precursor obtained in step a) is dried under a stream of        a neutral gas or under a stream of a gas containing oxygen at a        temperature below 200° C., and is calcined at a temperature        between 350 and 650° C.,    -   c) the dried and calcined precursor obtained in step b) is        impregnated with an impregnation solution comprising an yttrium        precursor,    -   d) the impregnated precursor obtained in step c) is dried under        a stream of a neutral gas or under a stream of a gas containing        oxygen at a temperature below 200° C., and is calcined at a        temperature between 350 and 650° C.

According to one variant, step a) comprises the following steps:

-   -   a1) a support comprising tin is prepared by introducing a tin        precursor during the forming of the support,    -   a2) the support containing tin obtained in step a1) is        impregnated with an impregnation solution comprising at least        one noble metal precursor and a phosphorus precursor.

According to another variant, step a) comprises the following steps:

-   -   a1′) a support comprising tin and phosphorus is prepared by        introducing a tin precursor and a phosphorus precursor during        the forming of the support,    -   a2′) the support containing tin and phosphorus obtained in step        a1′) is impregnated with an impregnation solution comprising at        least one noble metal precursor.

According to another variant, the catalyst obtained after step d) issubjected to a treatment under hydrogen.

The invention also relates to the use of the catalyst according to theinvention in a reforming process.

Hereinbelow, the groups of chemical elements are given according to theCAS classification (CRC Handbook of Chemistry and Physics, published byCRC Press, Editor in Chief D. R. Lide, 81^(st) edition, 2000-2001). Forexample, Group VIII according to the CAS classification corresponds tothe metals of columns 8, 9 and 10 according to the new IUPACclassification.

All the contents of the various components of the catalyst, and notablythe contents of noble metal, tin, phosphorus, yttrium and halogenatedcompound, are expressed relative to the element, unless explicitlyindicated otherwise.

DETAILED DESCRIPTION OF THE INVENTION

Catalyst

The invention relates to a catalyst comprising a support, at least onenoble metal M, tin, phosphorus and yttrium, the content of phosphoruselement being less than or equal to 1% by weight, and the content ofyttrium being less than or equal to 1% by weight relative to the mass ofthe catalyst.

The support generally comprises at least one oxide selected from thegroup consisting of magnesium, titanium, zirconium, aluminium andsilicon oxides. Preferably, the support comprises silica, alumina orsilica-alumina, and very preferably alumina. Preferably, the supportcomprises alumina, and very preferably the alumina is gamma-alumina.

The support advantageously has a total pore volume of between 0.1 and1.5 cm³/g, more preferably between 0.4 and 0.8 cm³/g. The total porevolume is measured by mercury porosimetry according to the standard ASTMD4284 with a wetting angle of 140°, as described in the book byRouquerol F.; Rouquerol J.; Singh K., “Adsorption by Powders & PorousSolids: Principle, Methodology and Applications”, Academic Press, 1999,for example by means of a Micromeritics™ brand Autopore III™ modelmachine.

The specific surface area of the support is advantageously between 50and 600 m²·g⁻¹, preferably between 100 and 400 m²·g⁻¹ and morepreferably between 150 and

300 m²·g⁻¹. The specific surface area is determined in the presentinvention by the BET method according to the standard ASTM D3663, methoddescribed in the same book cited above.

Advantageously, the support has a tapped packing density (TPD) value ofbetween 0.4 and 0.8 g/mL, preferably between 0.5 and 0.7 g/mL. The TPDmeasurement consists in introducing the support into a measuringcylinder (typically with a volume of 100 mL), the volume of which hasbeen determined beforehand, and then, by vibration, in tapping it untila constant volume is obtained. The bulk density of the tapped product iscalculated by comparing the mass introduced and the volume occupiedafter tapping. The measurement uncertainty is generally of the order of±0.01 g/mL.

Thus, when the support is used as a reforming catalyst support, it isable to meet the requirements of a “dense” support (e.g. tapped packingdensity of about 0.6 to 0.7 g/mL) and also the requirements of a “light”support (e.g. tapped packing density of about 0.5 to 0.6 g/mL).

Preferably, the tapped packing density (TPD) value of said support isbetween 0.5 and 0.7 g/mL.

The support is advantageously in the form of beads, extrudates, pelletsor powder. Preferably, the support is in the form of beads. The supportmay be obtained via any technique known to those skilled in the art. Theforming may be performed, for example, by extrusion, by pelletizing, bythe drop coagulation (oil drop) method, by granulation on a rotatingplate or via any other method that is well known to those skilled in theart.

When the support is in the form of beads, its diameter is generallybetween 0.5 and 5 mm. Such a bead may be manufactured via the oil-dropmethod. According to this method and when the support is an alumina, asuspension containing an alumina gel (such as boehmite (crystallinealuminium oxyhydroxide) or pseudoboehmite), an emulsifier, optionallymetal precursors and water is prepared and the suspension is transferredinto a dropping pot equipped with nozzles whose orifices are calibratedto form droplets. The suspension is then dripped by gravity into acolumn containing an organic phase in the upper part (petroleum phase)and a basic aqueous phase (ammoniacal solution) in the lower part, so asto collect the spheroidal particles at the bottom of the basic aqueousphase. It is during the passage of the droplet through the organic phasethat the forming of the spheres takes place, whereas gelation (orcoagulation) takes place in the aqueous phase. The beads are then driedand calcined. When the support is in the form of extrudates, they may beprepared by blending an alumina gel with water and suitable peptizers,such as hydrochloric acid or nitric acid, in the optional presence ofmetal precursors, until an extrudable paste is formed (shearing acidicblending). The paste obtained may be extruded through a die of suitablesize to form extrudates which are subsequently dried and then calcined.Prior to extrusion, it may sometimes be necessary to add a pHneutralizer such as an ammoniacal solution. In general, the diameter ofthe extrudates is between 0.5 and 5 mm, preferably with alength-to-diameter ratio of from 1:1 to 5:1.

An essential component of the catalyst according to the invention is anoble metal M, preferably platinum or palladium, very preferablyplatinum. This noble metal may exist in the final catalyst as oxide,sulfide, halide or oxyhalide compound in chemical combination with oneor more of the other components of the catalyst or in the form ofelemental metal.

The content of noble metal M in the catalyst according to the inventionis between 0.02% and 2% by weight, preferably between 0.05% and 1.5% byweight and even more preferably between 0.1% and 0.8% by weight relativeto the mass of the catalyst.

Another essential component of the catalyst according to the inventionis tin. This element may exist in the final catalyst as oxide, sulfide,halide or oxyhalide compound in chemical combination with one or more ofthe other components of the catalyst or in the form of elemental metal.

The tin content in the catalyst according to the invention is between0.005% and 10% by weight, more preferably between 0.01% and 5% by weightand very preferably between 0.1% and 1% by weight.

Another essential component of the catalyst according to the inventionis phosphorus. This element may exist in the final catalyst as oxide ormixed oxide, phosphate, polyphosphate, sulfide, halide, oxyhalide orhydride compound or in chemical combination with one or more of theother components of the catalyst.

The content of phosphorus element in the catalyst according to theinvention is less than or equal to 1% by weight, preferably between 0.3%and 1% by weight and particularly preferably between 0.4% and 0.8% byweight. Preferably, the phosphorus is added by impregnation.

Another essential component of the catalyst according to the inventionis yttrium. Yttrium may exist in the final catalyst as oxide, sulfide,halide or oxyhalide compound in chemical combination with one or more ofthe other components of the catalyst or in the form of elemental metal.

The content of yttrium element in the catalyst according to theinvention is less than or equal to 1% by weight, preferably between0.01% and 0.5% by weight and particularly preferably between 0.02% and0.3% by weight relative to the mass of the catalyst. Preferably, theyttrium is added by impregnation.

The simultaneous presence of an amount of phosphorus of less than orequal to 1% by weight, and preferably between 0.3% and 1% by weight, andof an amount of yttrium of less than or equal to 1% by weight relativeto the mass of the catalyst shows a surprising synergistic effect,notably for the essential functions of the catalyst, namely theselectivity and the stability, without deteriorating the activity.

The Sn/M atomic ratio is generally between 0.5 and 4.0, more preferablybetween 0.9 and 3.5 and very preferably between 0.95 and 3.2.

The P/M ratio is generally between 0.2 and 30.0, more preferably between0.5 and 20.0 and very preferably between 0.9 and 15.0.

The Y/M ratio is generally between 0.1 and 5.0 and more preferablybetween 0.2 and 3.0.

The catalyst according to the invention may also preferably comprise ahalogenated compound, selected from the group consisting of fluorine,chlorine, bromine and iodine. The content of halogenated compound isgenerally of between 0.1% and 8% by weight, preferably between 0.2% and3% by weight of catalyst after calcination. Preferably, the halogenatedcompound is chlorine.

The catalyst according to the invention may optionally also includeother promoters chosen from groups IA, IIA, IIIA (notably indium), IVA(notably germanium) and VA of the Periodic Table, cobalt, nickel, iron,tungsten, molybdenum, chromium, bismuth, antimony, zinc, cadmium andcopper. When these elements are present in the catalyst, the contentexpressed as oxide is generally between 0.01% and 2% by weight,preferably between 0.05% and 1% by weight relative to the mass of thecatalyst.

However, the catalyst preferably consists of a support, of at least onenoble metal M, of tin, of phosphorus and of yttrium, and particularlypreferably it consists of an alumina support, of platinum, of tin, ofphosphorus and of yttrium in the specific amounts of phosphorus andyttrium indicated above.

All the elements are preferably uniformly distributed in the support.

Catalyst Preparation Process

The catalyst according to the invention may be prepared according to anypreparation method known to those skilled in the art.

The noble metal may be incorporated into the support in any suitablemanner, such as coprecipitation, ion exchange or impregnation.Preferably, it is introduced by impregnation of the preformed support,for example by impregnation in excess or dry impregnation (the volume ofsolution containing the element to be introduced corresponding to thepore volume of the support), and preferably by impregnation in excess.To do this, the support is impregnated with an impregnation solutioncomprising at least the noble metal.

In general, hydrogen chloride or another similar acid may also be addedto the impregnation solution to further facilitate the incorporation orattachment to the surface of the support of the noble metal componentand uniform distribution of the metal components throughout the supportmaterial.

In addition, it is generally preferable to impregnate the support afterit has been calcined, so as to minimize the risk of leaching of thenoble metal.

When the noble metal is platinum, the platinum precursors form part ofthe following group, without this list being limiting:hexachloroplatinic acid, bromoplatinic acid, ammonium chloroplatinate,platinum chlorides, dichlorocarbonylplatinum dichloride,tetraammineplatinum chloride or dihydroxydiammineplatinum.Organoplatinum complexes, such as platinum(II) diacetylacetonate, mayalso be used. Preferably, the precursor used is hexachloroplatinic acid.

The tin may be incorporated into the support in any suitable manner,such as coprecipitation, ion exchange or impregnation, and in any stepof the process for preparing the catalyst.

According to a first variant, it may be introduced into the support, forexample during the synthesis of the support or during the forming of thesupport. Without being exhaustive, techniques for addition before orduring the dissolution of the oxide precursors of the support during thesynthesis of the support, with or without maturation, may be suitablefor use. The introduction may thus be simultaneous with or subsequent tothe mixing of the precursors of the support. The tin may be introducedduring the synthesis of the support according to any technique ofsol-gel type or may be added to an alumina sol. The tin may also beintroduced during the implementation of the support according to theprior art techniques of forming of the support, such as the formingprocedures by extrusion or by oil drop.

According to a second variant, the tin may be introduced onto thesupport, for example by impregnation of the preformed support.Impregnation of the support with a solution containing one or more tinprecursors may be performed with an excess of solution or by dryimpregnation. The impregnation may be performed in the presence ofspecies which act on the interaction between the tin precursor and thesupport. These species may be, for example, and without being limiting,mineral acids (HCl, HNO₃) or organic acids (such as carboxylic orpolycarboxylic acids), and organic compounds of complexing type, asdescribed, for example, in U.S. Pat. Nos. 6,872,300 and 6,291,394.Preferably, the impregnation is performed according to any techniqueknown to those skilled in the art for obtaining uniform distribution ofthe tin in the catalyst.

The tin precursors may be mineral or of organometallic type, optionallyof water-soluble organometallic type. The tin precursor may be chosenfrom the group formed by halogenated, hydroxide, carbonate, carboxylate,sulfate, tartrate and nitrate compounds. These tin forms may beintroduced into the medium for preparing the catalyst in their form assupplied or generated in situ (for example by introduction of tin andcarboxylic acid). The tin-based precursors of organometallic type maybe, for example, SnR₄, in which R represents alkyl group, for example abutyl group, Me₃SnCl, Me₂SnCl₂, Et₃SnCl, Et₂SnCl₂, EtSnCl₃, iPrSnCl₂,the hydroxides Me₃SnOH, Me₂Sn(OH)₂, Et₃SnOH, Et₂Sn(OH)₂, the oxide(Bu₃Sn)₂O or the acetate Bu₃SnOC(O)Me. Preferably, halogenated tinspecies, in particular chlorinated species, will be used. In particular,SnCl₂ or SnCl₄ will advantageously be used.

According to a third variant, the tin may also be introduced partlyduring the synthesis or forming of the support and partly by depositiononto the formed support.

Preferably, the tin is introduced into the support, i.e. during thesynthesis of the support or during the forming of the support. In thecase of an alumina-based support in the form of beads prepared by theoil drop technique, the tin precursor is introduced into the suspensionto be dripped.

The phosphorus may be incorporated into the support in any suitablemanner, such as coprecipitation, ion exchange or impregnation, and inany step of the process for preparing the catalyst. It may notably beintroduced according to the three variants described in the case of tin.

According to one variant, the phosphorus is introduced into the support,i.e. during its forming, for example simultaneously with the tin.

According to another variant, the phosphorus is introduced byimpregnation, and particularly preferably it is introduced byimpregnation at the same time as the noble metal. In this case, theimpregnation solution contains the noble metal precursor and thephosphorus precursor.

The phosphorus precursors may be acids or salts, for example H₃PO₄,H₃PO₃, H₃PO₂, NH₄H₂PO₄ or (NH₄)₂HPO₄, without this list beingexhaustive.

The yttrium may be incorporated into the support in any suitable manner,such as coprecipitation, ion exchange or impregnation, and in any stepof the process for preparing the catalyst. It may notably be introducedaccording to the three variants described in the case of tin.Preferably, it is introduced by impregnation, and particularlypreferably it is introduced after the noble metal has been introduced asdescribed below.

The yttrium precursor may be chosen from the group formed byhalogenated, hydroxide, carbonate, carboxylate, sulfate, tartrate andnitrate compounds. These yttrium forms may be introduced into the mediumfor preparing the catalyst in their form as supplied or generated insitu (for example by introduction of yttrium and carboxylic acid).Preferably, yttrium nitrate will be used, for example.

When other promoters are present, they may be incorporated into thesupport in any suitable manner, such as coprecipitation, ion exchange orimpregnation, and in any step of the process for preparing the catalyst.They may notably be introduced according to the three variants describedin the case of tin.

When several components of the catalyst are introduced into the support,i.e. during the synthesis of the support or during the forming of thesupport, the introduction may be simultaneous or may take placeseparately.

After introduction of the components into the support, the protocol forpreparing the catalysts according to the invention generally requiresdrying and calcination before the deposition of the noble metal andoptionally of other components. The drying is generally performed at atemperature of between 50° C. and 250° C., more preferably between 70°C. and 200° C., in air or under an inert atmosphere. The drying ispreferentially performed for a time of between 1 and 24 hours,preferably between 1 and 20 hours. The calcination is preferablyperformed at a temperature of between 350 and 650° C., preferablybetween 400 and 600° C. and even more preferably between 450 and 550°C., generally in air. The calcination time is generally between 30minutes and 16 hours, preferably between 1 hour and 5 hours. Thetemperature increase may be uniform or may include intermediate steadytemperature stages, these steady stages being reached with fixed orvariable temperature increase rates. These temperature increases maythus be identical or may differ in their rate (in degrees per minute orper hour).

When several components of the catalyst are introduced onto the supportformed by impregnation, the introduction of the components may besimultaneous by means of a single impregnation solution or may takeplace separately by means of several impregnation solutions containingone or more of the components, and may take place in any order.

Any impregnation solution described in the present invention maycomprise any polar solvent known to those skilled in the art. Said polarsolvent used is advantageously chosen from the group formed by methanol,ethanol, water, phenol and cyclohexanol, taken alone or as a mixture.Said polar solvent may also be advantageously chosen from the groupformed by propylene carbonate, DMSO (dimethyl sulfoxide),N-methylpyrrolidone (NMP) and sulfolane, taken alone or as a mixture.Preferably, a polar protic solvent is used. A list of common polarsolvents and also their dielectric constant may be found in the book“Solvents and Solvent Effects in Organic Chemistry” C. Reichardt,Wiley-VCH, 3rd edition, 2003, pages 472-474. Very preferably, thesolvent used is water or ethanol, and particularly preferably, thesolvent is water.

After each impregnation, the impregnated catalyst is generally dried soas to remove all or some of the solvent introduced during theimpregnation, preferably at a temperature of between 50° C. and 250° C.,more preferably between 70° C. and 200° C. The drying is preferentiallyperformed for a time of between 1 and 24 hours, preferably between 1 and20 hours. The drying is performed in air, or under an inert atmosphere(for example nitrogen).

After drying, the catalyst is generally calcined, generally in air. Thecalcination temperature is generally between 350 and 650° C., preferablybetween 400 and 650° C. and even more preferably between 450 and 550° C.The temperature ramp may optionally contain steady temperature stages.

The calcination time is generally between 30 minutes and 16 hours,preferably between 1 hour and 5 hours.

More particularly, the catalyst according to the invention may beprepared according to a preparation process comprising the followingsuccessive steps:

-   -   a) a precursor comprising a support, tin, phosphorus and a noble        metal is prepared,    -   b) the precursor obtained in step a) is dried under a stream of        a neutral gas or under a stream of a gas containing oxygen at a        temperature below 200° C., and is calcined at a temperature        between 350 and 650° C.,    -   c) the dried and calcined precursor obtained in step b) is        impregnated with an impregnation solution comprising an yttrium        precursor,    -   d) the impregnated precursor obtained in step c) is dried under        a stream of a neutral gas or under a stream of a gas containing        oxygen at a temperature below 200° C., and is calcined at a        temperature between 350 and 650° C.

It is preferable to introduce the yttrium onto a solid impregnated withthe noble metal, notably with platinum, and with phosphorus, which hasbeen dried and calcined beforehand. Specifically, introducing theyttrium after the noble metal and the phosphorus makes it possible toavoid any leaching of the yttrium during the impregnation, preferably inexcess, of the noble metal and of the phosphorus.

In step a), a support comprising tin, phosphorus and a noble metal isprepared.

The tin may be introduced at any moment in the preparation of thesupport, and preferentially during the forming, or by impregnation on analready-formed support. Preferably, the tin is introduced during theforming of the support.

This is likewise the case for the phosphorus. The phosphorus may beintroduced at any moment in the preparation of the support, andpreferentially during the forming, or by impregnation on analready-formed support. According to one variant, the phosphorus isintroduced into the support, i.e. during the forming of the support,preferably with the tin compound. According to another variant, thephosphorus is introduced by impregnation, and particularly preferably itis introduced by impregnation at the same time as the noble metal.

The introduction of the noble metal may advantageously be performed bymeans of one or more impregnations with an excess of solution onto thesupport, or by means of one or more dry impregnations, and preferably bya single impregnation in excess of said support (preferably containingthe tin compound and optionally the phosphorus), by means ofsolution(s), preferably aqueous solution(s), containing the noble metalprecursor and preferably the phosphorus precursor (when the support doesnot contain any or contains only part of the phosphorus).

Thus, according to a first variant, step a) comprises the followingsuccessive steps:

-   -   a1) a support comprising tin is prepared by introducing a tin        precursor during the forming of the support,    -   a2) the support containing tin obtained in step a1) is        impregnated with an impregnation solution comprising at least        one noble metal precursor and a phosphorus precursor.

According to a second variant, step a) comprises the followingsuccessive steps:

-   -   a1′) a support comprising tin and phosphorus is prepared by        introducing a tin precursor and a phosphorus precursor during        the forming of the support,    -   a2′) the support containing tin and phosphorus obtained in step        a1′) is impregnated with an impregnation solution comprising at        least one noble metal precursor.

In step b), the precursor obtained in step a) is dried and calcinedunder the conditions described above.

In step c), the dried and calcined precursor obtained in step b) isimpregnated with an impregnation solution comprising at least oneyttrium precursor. The introduction of yttrium may be advantageouslyperformed via one or more impregnations with an excess of solution onthe support, or preferably via one or more dry impregnations, and,preferably, via only one dry impregnation of said precursor, usingsolution(s), preferably aqueous solution(s), containing the yttriumprecursor.

In step d), the precursor obtained in step c) is dried and calcinedunder the conditions described above.

According to another variant, the catalyst according to the inventionmay be prepared by preparing a support comprising tin by introducing thetin precursor during the forming of the support, followed by one or moreimpregnations with an excess of solution onto the support, or by one ormore dry impregnations, and preferably by only one impregnation inexcess of said precursor, using solution(s), preferably aqueoussolution(s), containing a noble metal precursor, a phosphorus precursorand an yttrium precursor, alone or as a mixture, followed by drying andcalcination under the conditions described above.

When the various precursors used in the preparation of the catalystaccording to the invention do not contain halogen, or contain aninsufficient amount of halogen, it may be necessary to add a halogenatedcompound during the preparation. Any compound known to those skilled inthe art may be used and incorporated into any one of the steps forpreparing the catalyst according to the invention. In particular, it ispossible to use organic compounds such as methyl or ethyl halides, forexample dichloromethane, chloroform, dichloroethane, methylchloroform orcarbon tetrachloride.

The halogen may also be added by means of impregnation with an aqueoussolution of the corresponding acid, for example hydrochloric acid, atany point in the preparation. A typical protocol consists inimpregnating the solid so as to introduce the desired amount of halogen.The catalyst is kept in contact with the aqueous solution for a timethat is long enough to deposit this amount of halogen.

The chlorine may also be added to the catalyst according to theinvention by means of an oxychlorination treatment. Such a treatment maybe performed, for example, between 350 and 550° C. for several hoursunder a flow of air containing the desired amount of chlorine andoptionally containing water.

Before use, the catalyst is subjected to a treatment under hydrogen inorder to obtain an active metal phase. The procedure of this treatmentconsists, for example, of a slow increase of the temperature under astream of pure or dilute hydrogen, up to the maximum reductiontemperature, for example between 100 and 600° C. and preferably between200 and 580° C., followed by maintenance, for example for 30 minutes to6 hours at this temperature. This reduction may be performed immediatelyafter the calcination, or later by the user. It is also possible for theuser to directly reduce the dried product.

Catalytic Reforming Process

The invention also relates to a process for the catalytic reforming of ahydrocarbon-based feedstock in the presence of the catalyst according tothe invention. The catalyst according to the invention may indeed beused in processes for reforming gasolines and for producing aromaticcompounds.

The reforming processes make it possible to increase the octane numberof the gasoline fractions originating from the distillation of crude oiland/or from other refining processes, for instance catalytic cracking orthermal cracking. The processes for producing aromatics provide the baseproducts (benzene, toluene, xylenes) that can be used in thepetrochemical industry. These processes have an additional benefit,contributing to the production of large amounts of hydrogen, essentialfor refinery hydrotreating and hydrogenation processes.

The feedstock for the reforming processes generally contains paraffinic,naphthenic and aromatic hydrocarbons containing from 5 to 12 carbonatoms per molecule. This feedstock is defined, inter alia, by itsdensity and its weight composition. These feedstocks may have an initialboiling point of between 40° C. and 70° C. and a final boiling point ofbetween 160° C. and 220° C. They may also be formed by a gasolinefraction or a mixture of gasoline fractions having initial and finalboiling points of between 40° C. and 220° C. The feedstock may thus alsobe formed by a heavy naphtha having a boiling point of between 160° C.and 200° C.

Typically, the reforming catalyst is loaded into a unit and subjectedfirst to a reduction treatment as described above.

The feedstock is then introduced in the presence of hydrogen and with amole ratio of hydrogen/hydrocarbons of the feedstock generally ofbetween 0.1 and 10, preferably between 1 and 8. The operating conditionsof the reforming are generally as follows: a temperature preferablybetween 400° C. and 600° C., more preferably between 450° C. and 540°C., and a pressure preferably between 0.1 MPa and 4 MPa and morepreferably between 0.25 MPa and 3.0 MPa. All or some of the hydrogenproduced may be recycled to the inlet of the reforming reactor.

EXAMPLES

The examples that follow illustrate the invention.

Example 1: Preparation of a Pt/Al₂O₃—Sn—Cl Catalyst A1 (Comparative)

A boehmite was synthesized by basification of a 0.1 mol·L⁻¹ aluminiumnitrate solution with a 1 mol·L⁻¹ sodium hydroxide solution at roomtemperature and with the pH controlled at about 10. The suspension isthen matured for one week in an oven at 95° C. without stirring. The pHof the suspension after maturation changes: the final pH is equal to11.5. The solid is recovered by filtration and then washed in a volumeof water approximately equal to the starting volume. The solid isresuspended in water and treated in an autoclave at 150° C. for 4 hours.The suspension is centrifuged and then dried under a stream of air, atroom temperature.

The support of Example 1 is prepared using the boehmite thussynthesized. A suspension containing 25% of mineral material (expressedas percentage of Al₂O₃) is prepared by mixing a γ-alumina feed and theboehmite powder in an acidified aqueous solution containing 15% by massof HNO₃/Al₂O₃. Tin dichloride is added to this suspension so as toobtain 0.3% by weight of tin on the final solid. The solid fraction ofAl₂O₃ is provided to a proportion of 88% by weight by the boehmite andto a proportion of 12% by the γ-alumina feed. This suspension alsocontains a pore-forming agent and a surfactant. The pore-forming agentis an organic phase comprising a mixture of paraffins containing between10 and 12 carbon atoms, the boiling point of which is about 290° C. andthe density of which is 0.75 g/cm³. The surfactant is Galoryl™. Thesecompounds are introduced in the following proportions: mass fraction ofpore-forming agent/water=1.4% and mass fraction ofsurfactant/pore-forming agent=6%.

The system is subjected to stirring at 600 rpm until a suspension havingrheological properties suitable for being dropped is obtained (viscosity250 MPa·s).

Forming by oil dropping is performed. The dropping column is filled withan ammoniacal solution at a concentration of 28 g/L and an organicsolution consisting of the same petroleum cut as that used aspore-forming agent in the preparation of the emulsion. The suspension isdropped by means of calibrated nozzles. The beads are collected at thebottom of the column and placed in a ventilated oven at 120° C. in wetair containing 200 g of water/kg of dry air for 12 hours. They are thencalcined in dry air at 650° C. for 3 hours. The beads obtained have adiameter of 1.9 mm.

A catalyst A1 is prepared on this support, targeting a deposit of 0.3%by weight of platinum and 1% by weight of chlorine on the finalcatalyst. 400 cm³ of an aqueous solution of hexachloroplatinic acid andof hydrochloric acid are added to 100 g of alumina support containingtin. The support is left in contact with the solution for 4 hours and isthen drained. It is dried at 120° C. for 15 hours and then calcined at500° C. under a stream of air of 100 litres per hour for 3 hours, with atemperature increase rate of 7° C. per minute.

The chlorine content greater than 1% by weight after calcination isadjusted to 1% by weight by means of a partial dechlorination heattreatment at 520° C. in dry air supplemented with 8000 ppm by volume ofwater, for 2.5 hours.

Catalyst A1 obtained after dechlorination contains 0.29% by weight ofplatinum, 0.29% by weight of tin and 1.03% by weight of chlorine.

Example 2: Preparation of a Catalyst A2: Pt/Al₂O₃—Sn—P—Cl (Comparative)

A boehmite was synthesized by basification of a 0.1 mol·L⁻¹ aluminiumnitrate solution with a 1 mol·L⁻¹ sodium hydroxide solution at roomtemperature and with the pH controlled at about 10. The suspension isthen matured for one week in an oven at 95° C. without stirring. The pHof the suspension after maturation changes: the final pH is equal to11.5. The solid is recovered by filtration and then washed in a volumeof water approximately equal to the starting volume. The solid isresuspended in water and treated in an autoclave at 150° C. for 4 hours.The suspension is centrifuged and then dried under a stream of air, atroom temperature.

The support of Example 2 is prepared using the boehmite thussynthesized. A suspension containing 25% of mineral material (expressedas percentage of Al₂O₃) is prepared by mixing a γ-alumina feed and theboehmite powder in an acidified aqueous solution containing 15% by massof HNO₃/Al₂O₃. Tin dichloride and phosphoric acid are simultaneouslyadded to this suspension so as to obtain 0.3% by weight of tin and 0.4%by weight of phosphorus on the final solid. The solid fraction of Al₂O₃is provided to a proportion of 88% by weight by the boehmite and to aproportion of 12% by the γ-alumina feed. This suspension also contains apore-forming agent and a surfactant. The pore-forming agent is anorganic phase comprising a mixture of paraffins containing between 10and 12 carbon atoms, the boiling point of which is about 290° C. and thedensity of which is 0.75 g/cm³. The surfactant is Galoryl™. Thesecompounds are introduced in the following proportions: mass fraction ofpore-forming agent/water=1.4% and mass fraction ofsurfactant/pore-forming agent=6%.

The system is subjected to stirring at 600 rpm until a suspension havingrheological properties suitable for being dropped is obtained (viscosity250 MPa·s).

Forming by oil dropping is performed. The dropping column is filled withan ammoniacal solution at a concentration of 28 g/L and an organicsolution consisting of the same petroleum cut as that used aspore-forming agent in the preparation of the emulsion. The suspension isdropped by means of calibrated nozzles. The beads are collected at thebottom of the column and placed in a ventilated oven at 120° C. in wetair containing 200 g of water/kg of dry air for 12 hours. They are thencalcined in dry air at 650° C. for 3 hours. The beads obtained have adiameter of 1.9 mm.

A catalyst A is prepared on this support, targeting a deposit of 0.3% byweight of platinum and 1% by weight of chlorine on the final catalyst.400 cm³ of an aqueous solution of hexachloroplatinic acid and ofhydrochloric acid are added to 100 g of alumina support containing tin.The support is left in contact with the solution for 4 hours and is thendrained. It is dried at 120° C. for 15 hours and then calcined at 500°C. under a stream of air of 100 litres per hour for 3 hours, with atemperature increase rate of 7° C. per minute. The chlorine contentgreater than 1% by weight after calcination is adjusted to 1% by weightby means of a partial dechlorination heat treatment at 520° C. in dryair supplemented with 8000 ppm by volume of water, for 2.5 hours.

Catalyst A obtained after dechlorination contains 0.29% by weight ofplatinum, 0.28% by weight of tin, 0.40% by weight of phosphorus and1.01% by weight of chlorine.

Example 3: Preparation of a Catalyst B: YPt/Al₂O₃—Sn—Cl (Comparative)

The support of Example 3 is prepared in a similar manner to that ofExample 2, except that only tin dichloride is added to the boehmitesuspension, to target 0.3% by weight of tin in the final solid.

Impregnation with an excess of platinum is performed on this support,targeting a deposit of 0.3% by weight of platinum and 1% by weight ofchlorine on the final catalyst, in the same manner as described inExample 2.

After calcination, dry impregnation of yttrium nitrate is performed totarget 0.09% by weight on the final catalyst. Before impregnation of theY, the catalyst is left in a water-saturated atmosphere overnight atroom temperature. 42 cm³ of an aqueous solution of yttrium nitrate areadded to 70 g of alumina support containing tin. The support is left incontact with the solution for 30 minutes. After impregnation, the solidis left again overnight to mature at room temperature in awater-saturated atmosphere. It is dried at 120° C. for 15 hours and thencalcined at 500° C. under a stream of air of 100 litres per hour for 3hours, with a temperature increase rate of 7° C. per minute. Adjustmentof the chlorine content is performed as described in Example 2, for 2hours.

Catalyst B obtained after dechlorination contains 0.29% by weight ofplatinum, 0.31% by weight of tin, 0.09% by weight of yttrium and 1.00%by weight of chlorine.

Example 4: Preparation of a Catalyst C: YPt/Al₂O₃—Sn—P_(0.4)—Cl(According to the Invention)

A catalyst C is prepared from the support of Example 2 containing 0.3%by weight of tin and 0.4% by weight of phosphorus, by impregnation ofplatinum and then of yttrium as described in Example 3.

Catalyst C obtained after dechlorination contains 0.32% by weight ofplatinum, 0.08% by weight of yttrium, 0.29% by weight of tin, 0.419% byweight of phosphorus and 1.04% by weight of chlorine.

Example 5: Preparation of a Catalyst D: YPt/Al₂O₃—Sn—P_(0.8)—Cl(According to the Invention)

The support of Example 5 is prepared in a similar manner to that ofExample 2, except that the target phosphorus content is 0.8% by weighton the final catalyst.

Platinum and then yttrium are subsequently impregnated as described inExample 2.

Catalyst D obtained after dechlorination contains 0.29% by weight ofplatinum, 0.08% by weight of yttrium, 0.29% by weight of tin, 0.76% byweight of phosphorus and 1.01% by weight of chlorine.

Example 6: Preparation of a Catalyst E: PtY/Al₂O₃—Sn—P_(0.4)—Cl(According to the Invention)

A catalyst E is prepared from the support of Example 2 containing 0.3%by weight of tin and 0.4% by weight of phosphorus, by impregnation ofyttrium and then of platinum, which differs from Example 3 in the orderof introduction by impregnation of the elements. The target contents of0.08% by weight of yttrium and 0.30% by weight of platinum areidentical.

Catalyst E obtained after dechlorination contains 0.31% by weight ofplatinum, 0.07% by weight of yttrium, 0.30% by weight of tin, 0.38% byweight of phosphorus and 0.98% by weight of chlorine.

Example 7: Preparation of a Catalyst F: YPt/Al₂O₃—Sn—P_(0.3)—Cl(According to the Invention)

The support of Example 7 is prepared in a similar manner to that ofExample 2, except that the target phosphorus content is 0.3% by weighton the final catalyst.

Platinum and then yttrium are subsequently impregnated as described inExample 3.

Catalyst F obtained after dechlorination contains 0.29% by weight ofplatinum, 0.07% by weight of yttrium, 0.31% by weight of tin, 0.31% byweight of phosphorus and 1.04% by weight of chlorine.

Example 8: Preparation of a Catalyst G: YPt/Al₂O₃—Sn—P_(1.15)—Cl(Comparative)

The support of Example 8 is prepared in a similar manner to that ofExample 2, except that the target phosphorus content is 1.15% by weighton the final catalyst.

Platinum and then yttrium are subsequently impregnated as described inExample 2.

Catalyst G obtained after dechlorination contains 0.30% by weight ofplatinum, 0.08% by weight of yttrium, 0.31% by weight of tin, 1.17% byweight of phosphorus and 0.97% by weight of chlorine.

Example 9: Preparation of a Catalyst H: YPt/Al₂O₃—Sn—P_(0.4)—Cl(According to the Invention)

A catalyst H is prepared from the support of Example 2 containing 0.3%by weight of tin and 0.4% by weight of phosphorus, by impregnation ofplatinum and then of yttrium as described in Example 3, the differencebeing that the target yttrium content is 0.50% by weight.

Catalyst H obtained after dechlorination contains 0.30% by weight ofplatinum, 0.48% by weight of yttrium, 0.30% by weight of tin, 0.39% byweight of phosphorus and 1.01% by weight of chlorine.

Example 10: Preparation of a Catalyst I: YPtP_(0.4)/Al₂O₃—Sn—Cl(According to the Invention)

The support of Example 3 is prepared in a similar manner to that ofExample 2, except that only tin dichloride is added to the boehmitesuspension, to target 0.3% by weight in the final solid.

Impregnation with an excess of platinum is performed according toExample 2, except that phosphoric acid is added to thehexachloroplatinic acid solution so as to target a content of 0.4% byweight on the final catalyst. The dry impregnation of yttrium isperformed according to the procedure described in Example 3. The heattreatments are identical to those of Example 3.

Catalyst I obtained after dechlorination contains 0.291% by weight ofplatinum, 0.08% by weight of yttrium, 0.31% by weight of tin, 0.38% byweight of phosphorus and 1.03% by weight of chlorine.

Example 11: Preparation of a Catalyst J: YPtP_(0.4)/Al₂O₃—Sn—Cl(Comparative)

Catalyst J is prepared exactly like catalyst H, but with a differenttarget content of Y (higher) of the order of 1.2% by weight. Catalyst Jobtained after dechlorination contains 0.29% by weight of platinum,1.17% by weight of yttrium, 0.29% by weight of tin, 0.38% by weight ofphosphorus and 0.98% by weight of chlorine.

Example 12: Evaluation of the Performance of Catalysts A1, A2 and B to Jin Catalytic Reforming

Samples of the catalysts whose preparations are described in Examples 1to 11 were used in a reaction bed adapted to the conversion of ahydrocarbon-based feedstock, of naphtha type obtained from oildistillation. This naphtha has the following composition:

-   -   49.6% by weight of paraffinic compounds,    -   35.3% by weight of naphthenes,    -   15.1% by weight of aromatic compounds.

For a total density of 0.7539 g/cm³. The initial and final distillationpoints of this feedstock are 101 and 175° C., respectively, with 95% ofthe distillation performed at 166° C.

The research octane number is close to 55.

After loading into the reactor, the catalysts are activated by heattreatment under an atmosphere of pure hydrogen, for a time of 2 hours at490° C.

Evaluation of the catalytic performance is performed under reformingreaction conditions, in the presence of hydrogen and naphtha describedabove. The conditions for the implementation of the catalyst are asfollows:

-   -   Pressure of the reactor: 0.76 MPa (7.6 barg)    -   Feedstock flow rate of 1.8 kg/hour per kg of catalyst    -   Hydrogen/feedstock hydrocarbons mole ratio: 3

The comparison of the catalysts is performed at an equivalent quality ofresearch octane number (RON) of the liquid effluents (reformates)resulting from the catalytic conversion of the feedstock. The comparisonis performed for a RON of 100.

The selectivity is expressed as yield of C₅₊ compounds expressed as amass percentage relative to the effluent at a given level of activity.During the test, the yield passes through a first phase during which itincreases with the time under feedstock which corresponds to theselectivation of the catalyst by the coke. Next, after a steady stage ofvariable duration, the yield values decrease with time. This is theperiod of deactivation of the catalyst. The comparisons of catalysts interms of selectivity will be made here using the yield values measuredover the steady stages. The accuracy of this measurement is ±0.3 point.A selective catalyst is expressed by a high C5+ yield. The activity isexpressed by a temperature required to reach a given octane number (alsoknown as the RON or Research Octane Number). Here, the temperature willbe taken at 24 hours of testing. The accuracy of this measurement is ±2°C. A very active catalyst is expressed by a relatively low temperatureto reach the RON.

The term “stability” means the stability of the activity which isgenerally measured by the thermal increment applied per unit of time tomaintain a constant RON of 100. A stable catalyst is expressed by a lowthermal increment.

Temper- Thermal Yield ature increment C5+ at 24 over (weight hours 240hours Catalyst %) (° C.) (° C./h) A1 Pt/Al₂O₃—Sn—Cl 86.8 475 0.17 A2Pt/Al₂O₃—Sn—P_(0.4)—Cl 88.4 481 0.12 B Y_(0.1)Pt/Al₂O₃—Sn—Cl 88.6 4780.10 C Y_(0.1)Pt/Al₂O₃—Sn—P_(0.4)—Cl 89.0 481 0.08 DY_(0.1)Pt/Al₂O₃—Sn—P_(0.8)—Cl 89.2 484 0.07 EPtY_(0.1)/Al₂O₃—Sn—P_(0.4)—Cl 89.0 482 0.08 FY_(0.1)Pt/Al₂O₃—Sn—P_(0.3)—Cl 88.7 480 0.10 GY_(0.1)Pt/Al₂O₃—Sn—P_(1.15)—C 88.9 486 0.06 HY_(0.5)Pt/Al₂O₃—Sn—P_(0.4)—Cl 88.8 485 0.09 IY_(0.1)PtP_(0.4)/Al₂O₃—Sn—Cl 89.6 480 0.07 JY_(1.2)Pt/Al₂O₃—Sn—P_(0.4)—Cl 88.7 489 0.13

These results show a synergistic effect between P and Y when thephosphorus content is less than or equal to 1% by weight and the yttriumcontent is less than or equal to 1% by weight of yttrium. This effectmakes it possible to improve the selectivity and the stability of thecatalysts without degrading their activity.

The invention claimed is:
 1. Catalyst comprising: a support, at leastone noble metal M, tin, and phosphorus, and only one metallic promoterwherein the metallic promoter is yttrium, wherein the phosphorus contentis between 0.3% and 1% by weight relative to the mass of the catalyst,and wherein the yttrium content is between 0.01% and 0.5% by weightrelative to the mass of the catalyst.
 2. The catalyst according to claim1, wherein the content of noble metal M is between 0.02% and 2% byweight relative to the mass of the catalyst.
 3. The catalyst accordingto claim 1, wherein the metal M is platinum or palladium.
 4. Thecatalyst according to claim 1, wherein the tin content is between 0.005%and 10% by weight relative to the mass of the catalyst.
 5. The catalystaccording to claim 1, wherein the yttrium content is between 0.01% and0.5% by weight relative to the mass of the catalyst.
 6. The catalystaccording to claim 1, wherein the Sn/M atomic ratio is between 0.5 and4.0, the P/M ratio is between 0.2 and 30.0 and the Y/M ratio is between0.1 and 5.0.
 7. The catalyst according to claim 1, wherein the supportcomprises silica, alumina or silica-alumina.
 8. The catalyst accordingto claim 1, additionally comprising a halogenated compound.
 9. Thecatalyst according to claim 8, wherein the content of halogenatedcompound is between 0.1% and 8% by weight relative to the mass of thecatalyst.
 10. The catalyst according to claim 1, wherein the yttriumcontent is between 0.07 to 0.48% by weight relative to the mass of thecatalyst.
 11. The catalyst according to claim 1, wherein the phosphorouscontent is between 0.3 to 0.8%, by weight relative to the mass of thecatalyst.
 12. The catalyst according to claim 1, wherein the phosphorouscontent is between 0.3 to 0.8%, by weight relative to the mass of thecatalyst.
 13. The catalyst according to claim 1, wherein the phosphorouscontent is between 0.4 to 0.8%, by weight relative to the mass of thecatalyst.
 14. The catalyst according to claim 1, wherein the wherein theyttrium content is between 0.01% and 0.5%, by weight relative to themass of the catalyst.
 15. The catalyst according to claim 1, wherein thephosphorus content is between 0.4% and 0.8% by weight relative to themass of the catalyst, the yttrium content is between 0.01% and 0.5%, byweight relative to the mass of the catalyst, the tin content is between0.01% and 1% by weight relative to the mass of the catalyst, and whereinthe noble metal is platinum and the platinum content is between 0.1% and0.8%.
 16. The catalyst according to claim 1, wherein the catalystconsists of a support, at least one noble metal M, tin, and phosphorus,only one metallic promoter wherein the metallic promoter is yttrium, anda halogenated compound wherein the tin content is between 0.005% and 10%by weight relative to the mass of the catalyst, wherein the phosphoruscontent is between 0.3% and 1% by weight relative to the mass of thecatalyst, and wherein the yttrium content is between 0.01% and 0.5% byweight relative to the mass of the catalyst.
 17. The catalyst of claim 1wherein the catalyst is prepared by a process comprising the followingsuccessive steps: a) a precursor comprising a support, tin, phosphorusand the noble metal is prepared, b) the precursor obtained in step a) isdried under a stream of a neutral gas or under a stream of a gascontaining oxygen at a temperature below 200° C., and is calcined at atemperature between 350 and 650° C., c) the dried and calcined precursorobtained in step b) is impregnated with an impregnation solutioncomprising an yttrium precursor, d) the impregnated precursor obtainedin step c) is dried under a stream of a neutral gas or under a stream ofa gas containing oxygen at a temperature below 200° C., and is calcinedat a temperature between 350 and 650° C.
 18. A catalyst comprising: asupport, at least one noble metal M, tin, and phosphorus, and only onemetallic promoter wherein the metallic promoter is yttrium, thephosphorus content being between 0.3% and 1.15% by weight relative tothe mass of the catalyst, the yttrium content being less than or equalto 1% by weight relative to the mass of the catalyst and wherein thecatalyst has a thermal increment applied per unit of time to maintain aconstant research octane number of 100 wherein the thermal incrementover 240 hours is equal to or less than 0.10 (° C./h).